What Is Thyroid Cancer?

Cancer happens when cells in the body change and grow out of control. These cells can form lumps of tissue called tumors. Cancer that starts in cells of the thyroid is called thyroid cancer.

Understanding the thyroid

The thyroid is a small, butterfly-shaped gland in front of the neck, just below the Adam's apple. The thyroid controls the rate at which every part of the body works. This is called metabolism. The thyroid gland regulates the metabolism by making thyroid hormone, a chemical that carries messages from the thyroid to the rest of the body through the bloodstream. The thyroid also makes the hormone called calcitonin. This regulates how calcium is used in the body.

When thyroid cancer forms

Cells in the thyroid may grow out of control, forming small lumps called nodules. But most thyroid nodules are not cancer. The thyroid may also enlarge (swell). Thyroid cancer can spread from the thyroid to other parts of the body. This spread is called metastasis. In general, the more cancer spreads, the harder it is to treat.

There are four main types of thyroid cancer (also called thyroid carcinoma):

Papillary carcinoma, which is the most common type

Follicular carcinoma

Medullary thyroid carcinoma

Anaplastic carcinoma

Treatment choices for thyroid cancer

There are different types of thyroid cancer. You and your healthcare provider will discuss a treatment plan that is based on your type of cancer and your personal needs. Treatment choices may include: